In the medical arts, it is often necessary to effect both pneumatic connections and electrical connections between an in vivo medical device and a control apparatus which is outside the patient's body. It can be readily appreciated that it can be time-consuming and labor-intensive for medical personnel to identify each individual fluid line and electrical lead from an in vivo device and then connect each fluid line or electrical lead to its corresponding mating part on the control apparatus.
As one example, U.S. Pat. No. 4,989,456 to Stupecky, assigned to the same assignee as the present invention, discloses a flow meter which is intended to be connected to the airway of a patient to measure the patient's air flow rate. Monitoring of respiratory air flow in critical care patients and in patients during anesthesia is very important for correctly assessing the patient's condition and for selecting the course of future treatment. In accordance with the Stupecky invention, the flow meter has two ports. Each port is placed in fluid communication with a control apparatus external to the patient for converting the pneumatic signals from the ports into an electrical signal representative of the patient's air flow. Thus, it is necessary to provide a means for connecting the flow meter to the control apparatus.
Furthermore, demand has increased in the medical industry for relatively inexpensive, disposable sensors. Disposable sensors are required to reduce the requirement for and cost of sterilization, which is necessary to reduce the risk of transmitting infectious diseases, e.g., AIDS. Unfortunately, many applications require that in vivo sensors be capable of attaining accuracies on the order of a few per cent, in order to be diagnostically useful. This means that many sensors, such as the flow meter disclosed by Stupecky, must either be made within relatively precise manufacturing tolerances to avoid the need for calibration, which makes such flow meters expensive, or must be calibrated bedside prior to each use of the flow meter, which is labor-intensive and often impractical. Under these alternatives, the cost of making or calibrating the flow meter can be prohibitive, particularly in view of the requirement that the flow meter preferably be disposable. The problem of expense in order to ensure accuracy is particularly acute in the case of flow meters.
As another example of a device which requires multiple fluid and electrical connections to a control apparatus, certain medical catheters are used for both the introduction of liquids into the body, and the measurement of pressure and temperature in different parts of the body. One such device, known as an esophageal catheter, is disclosed in U.S. Pat. No. 4,214,593, entitled "Esophageal Pressure Monitoring Device". This patent describes a balloon catheter for measurement of esophageal pressures of patients with respiratory problems. For these measurements, pneumatic lines connect an external monitoring and testing instrument to the balloon cuff positioned within the patient's stomach.
Additionally, a pH probe or a thermistor can also be advantageously mounted within the esophageal catheter so that it is inserted into the esophagus of the patient when the distal end of the catheter is located within the esophagus. Electrical wires connected to the pH probe or thermistor are connected to instruments external to the patient. In the case of a thermistor, a resistance variation of the thermistor occurs in accordance with the body temperature change of the patient and is connected by the monitoring instrument to a measurement of body temperature.
Thus, in this type of medical apparatus, it is necessary to connect both pneumatic and electrical lines from the patient's body to a monitoring instrument, in this example a cardiopulmonary monitor. Since these medical catheters are typically discarded after a single patient use, the cost of connector must be kept to a minimum without sacrificing reliability.
Further, as was the case with the flow meter discussed above, not just any pH probe or thermistor can be attached to the prior art multi-purpose catheters for providing an accurate pH or temperature indications. This is because many pH probes and thermistors, particularly inexpensive probes and thermistors, have relatively large accuracy tolerances. Consequently, relatively expensive pH probes and thermistors that do not require extensive calibration prior to use have conventionally been used on many of the multiple function catheters mentioned above.
Conventionally, separate connectors are employed for each of the plural pneumatic lumens and the electric wires. Typically, separate luer connectors are used for each pneumatic or fluidic connector, the luer connector including a male tapered tubular part which fits into a female tapered socket. These parts are locked together by rotating a threaded sleeve which is concentric with the tubing being connected. The engagement force between the two parts thus depends upon the torque exerted by the user, resulting in a wide range of engagement forces. By way of example, in the case of plastic luer fittings, the engagement of mating parts can vary by as much as 0.05 inches. Moreover, this locking sleeve can generate substantial axial force which is, in turn, magnified by the effect of the taper of the female socket.
The luer connector has several disadvantages. First, the contact pressure in the connector is determined by the strength of the operator who screwed in the connector; therefore, contact pressure is not constant and thus the contact reliability is low if insufficient torque is used. If, however, the luer connector is tightened with too much torque, it is often very difficult to later unscrew and disconnect the fluidic lines. Second, it is not easy to connect together or disconnect the luer connection since it requires a screwing in and screwing out motion. The problem is particularly exacerbated when several fluidic lines have to be connected. Third, as noted above, the luer connector is not adapted for multiple port connections with a single connector because of the high insertion forces and need for a separate locking means for each individual part. Connecting multiple parts is time consuming and tedious for the user who needs to correctly identify each individual fluidic line and connect it to its proper mating part. A mistake on the part of the user in connecting multiple fluidic lines with luer connectors renders inoperable the device being connected and possibly could be detrimental to the health of the patient. Further, conventional luer connectors are not cost effective when used with disposable medical products such as a disposable catheter.